From c11b2426df5b150684d9a672801effa646be8723 Mon Sep 17 00:00:00 2001
From: hoenicke <hoenicke@379699f6-c40d-0410-875b-85095c16579e>
Date: Fri, 15 Feb 2002 15:22:50 +0000
Subject: [PATCH] Handle empty blocks used for "while(true) {}"

git-svn-id: https://svn.code.sf.net/p/jode/code/trunk@1362 379699f6-c40d-0410-875b-85095c16579e
---
 jode/ChangeLog                                | 11 ++++++
 .../sf/jode/bytecode/BasicBlockReader.java    | 35 ++++++++++++++-----
 .../sf/jode/decompiler/MethodAnalyzer.java    | 10 +++---
 3 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/jode/ChangeLog b/jode/ChangeLog
index 8a2d1d4..aecd9a1 100644
--- a/jode/ChangeLog
+++ b/jode/ChangeLog
@@ -1,3 +1,14 @@
+2002-02-15  Jochen Hoenicke  <jochen@gnu.org>
+
+	* net/sf/jode/bytecode/BasicBlockReader.java: handle empty loops.
+	(IS_NULL): new constant to tag empty blocks.
+	(markReachableBlocks): check for empty loops. 
+	(convertBlock): Handle empty blocks.
+	(convert): Handle IS_NULL.
+
+	* net/sf/jode/decompiler/MethodAnalyzer.java:
+	(analyzeCode): handle empty blocks.
+
 2001-08-14  Jochen Hoenicke  <jochen@gnu.org>
 
 	* build.xml: test is default.
diff --git a/jode/src/net/sf/jode/bytecode/BasicBlockReader.java b/jode/src/net/sf/jode/bytecode/BasicBlockReader.java
index b388658..da2a49a 100644
--- a/jode/src/net/sf/jode/bytecode/BasicBlockReader.java
+++ b/jode/src/net/sf/jode/bytecode/BasicBlockReader.java
@@ -39,6 +39,7 @@ class BasicBlockReader implements Opcodes {
     static final int IS_REACHABLE = 2;
     static final int IS_FORWARD   = 4;
     static final int IS_CATCHER   = 8;
+    static final int IS_NULL      = 16;
 
     private class InstrInfo {
 	Instruction instr;
@@ -97,9 +98,21 @@ class BasicBlockReader implements Opcodes {
 		&& (info.instr.getOpcode() == opc_goto
 		    || (info.instr.getOpcode() == opc_return
 			&& info.stack == 0))) {
-		/* This is a forward block.
+		/* This is a forward block.  We need to check for loops,
+		 * though.
 		 */
-		info.flags |= IS_FORWARD;
+		InstrInfo succ = info;
+		do {
+		    if (succ.instr.getOpcode() == opc_return) {
+			succ = null;
+			break;
+		    }
+		    succ = infos[info.succs[0]];
+		} while ((succ.flags & IS_FORWARD) != 0);
+		if (succ == info)
+		    info.flags |= IS_NULL;
+		else
+		    info.flags |= IS_FORWARD;
 	    } else {
 		// Check for reachable exception handlers
 		for (int i=0; i < handlers.length; i++) {
@@ -240,15 +253,15 @@ class BasicBlockReader implements Opcodes {
 
     private void convertBlock(int firstAddr, int count) {
 	Instruction[] instrs = new Instruction[count];
-
 	InstrInfo info = infos[firstAddr];
 	int blockNr = info.blockNr;
-	instrs[0] = info.instr;
-	for (int i=1; i < count; i++) {
-	    info = infos[info.nextAddr];
+
+	for (int i = 0; i < count; i++) {
+	    if (i > 0)
+		info = infos[info.nextAddr];
 	    instrs[i] = info.instr;
 	}
-
+	
 	int[] lastSuccs = info.succs;
 	int succLength = lastSuccs != null ? lastSuccs.length : 0;
 	boolean alwaysJump = info.instr.doesAlwaysJump();
@@ -292,8 +305,12 @@ class BasicBlockReader implements Opcodes {
 		start = -1;
 	    }
 	    if ((info.flags & (IS_REACHABLE | IS_FORWARD)) == IS_REACHABLE) {
-		start = i;
-		count = 0;
+		if ((info.flags & IS_NULL) != 0) {
+		    convertBlock(i, 0);
+		} else {
+		    start = i;
+		    count = 0;
+		}
 	    }
 	    if (start != -1)
 		count++;
diff --git a/jode/src/net/sf/jode/decompiler/MethodAnalyzer.java b/jode/src/net/sf/jode/decompiler/MethodAnalyzer.java
index 6c593a7..91c8148 100644
--- a/jode/src/net/sf/jode/decompiler/MethodAnalyzer.java
+++ b/jode/src/net/sf/jode/decompiler/MethodAnalyzer.java
@@ -475,9 +475,8 @@ public class MethodAnalyzer implements Scope, ClassDeclarer {
 	    int count = 0;
 	    for (int i=0; i < blocks.length; i++) {
 		int mark = 100;
-		int last = blocks[i].getInstructions().length - 1;
-		for (int j=0; j <= last; j++) {
-		    Instruction instr = blocks[i].getInstructions()[j];
+		Instruction[] instrs = blocks[i].getInstructions();
+		for (int j=0; j < instrs.length; j++) {
 		    if (GlobalOptions.verboseLevel > 0 && j > mark) {
 			GlobalOptions.err.print('.');
 			mark += 100;
@@ -487,11 +486,12 @@ public class MethodAnalyzer implements Scope, ClassDeclarer {
 			pl.updateProgress(done, methodName);
 			count = 0;
 		    }
-		    Opcodes.addOpcode(flows[i], instr, this);
+		    Opcodes.addOpcode(flows[i], instrs[j], this);
 		}
 		Block[] succs = blocks[i].getSuccs();
 		FlowBlock[] flowSuccs;
-		int lastOpcode = blocks[i].getInstructions()[last].getOpcode();
+		int lastOpcode = instrs.length > 0
+		    ? instrs[instrs.length-1].getOpcode() : Opcodes.opc_nop;
 		if (lastOpcode >= Opcodes.opc_ireturn
 		    && lastOpcode <= Opcodes.opc_areturn) {
 		    flowSuccs = new FlowBlock[] { FlowBlock.END_OF_METHOD };